When I say it's "we could start a colony at Alpha Centauri with current or conceivable technology", wiggin, what I mean it is not actually physically impossible for us to do it, not that I think such an undertaking is likely or even a good idea.

If aliens showed up tomorrow and issued an ultimatum: "This is getting ridiculous now; If don't at least have a colony on Alpha Centauri by 2200 we're going to exterminate you. You're making the whole galaxy look bad." and we just devoted like 25% of the entire planet's GDP to making it happen, it could be done. That's what I mean, not that I think a project like that would happen under any realistic economic and political constraints.

But the fact that it's a theoretical possibility even now has implications for assessing how difficult it it would be for a vastly more advanced society than our own.

The other caveat is that it all rather depends on the presence of an Earthlike planet within approximately 20 lightyears with a reasonably non-hostile biosphere. No point going to Alpha Centauri to colonize a hellhole when we have so many hellholes much closer to hand.

If propulsion gets dramatically better, it will at least be feasible, even if ruinously expensive, to set up a colony. But absent a lot of other fundamental shifts in technology, there's no way it's going to appear to be worth it.

I can't really envisage a future where we get vastly better propulsion but all other technologies stay exactly the same. Now *that* would be science fiction, which is a genre where, apparently, future societies have mastered the reality bending physics of FTL travel, and the engineering challenges involved in constructing miles long space warships but everyone's day to day lives are more or less identical to the present day, perhaps even absent day to day conveniences like smartphones or the internet. (Somewhat off-topic but it's a pet peev so fuck it)

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We *are* one of the first races out of the gate; the universe is only 14 billion years old and most models of the ultimate fate of the universe have it remaining this way for at least tens of billions and possibly trillions more. Assuming those models are correct, we're in a very young universe.

Looked at that way, sure. But I meant that it's been billions of years since life such as ours should have been possible. Our star formed a few billion years later that a star like it could have, and we took a couple billion years longer evolving than we theoretically could have. So if sapient life is common, then there should be races in the galaxy with a couple billion years head start on us, more than enough time to fill it at even a sluggish pace.

The more I think about it the more sense it makes, our science has already begun shown us that the reality we perceive in our day to day lives and the reality as it actually exists are not the same thing, and questions such as why the universe exists and is the way it is are currently completely beyond us; it makes sense that as a civilisation advances in knowledge over a period of millions of years they will come to understand our reality in ways we cannot even comprehend and will, presumably, also develop technology anchored in that understanding.

A singularity or a vastly different way of life would probably be a perfectly good reason not to head out into the stars. Why colonize the galaxy when you can hop into a pocket universe instead, or you're all uploaded to an infinite capacity mainframe housed in a microsingularity, or you can make TARDISes arbitrarily bigger on the inside? Or some explanation that no human is even capable of thinking of.

An related idea is that intersteller colonisation *is* a good idea until you reach a certain point of development at which point it stops becoming a worthwhile endeavour. This may happen in fits and starts. For example:

* Interseller colonisation is current theoretically possible but very expensive so not worthwhile
* Technology develops; now it's worthwhile because it's cheaper and we're running out of living space
* A few hundred years later and now technology has developed to the point where we can build things like Halos/Culture orbitals and other elaborate megastructures to live on, so we don't need to expand into other stellar systems for more living space; we still do it sometimes just for the hell of it but there's no massive push to expand as there was in previous eras and expansion slows to a crawl
* Thousands of years later our society is so fantastically advanced we now need dyson spheres to meet our energy needs so we have to start expanding other stars again to meet our resource needs.
* Perhaps a million years on we're now so advanced we can now manipulate reality itself and everyone just moves into the giant Tardis we made

For the record, I wrote my TARDIS example before I read yours

This actually works I think. As long as colonization has constraints, it'd fit without resorting to low-probability scenarios while still allowing relatively common sapience.

I forgot to write that I think artificial habitats are a more realistic prospect for human space habitation than living on planetary surfaces, in this or any other system.

P.S. if you put engines on a space habitat now it's called a generation ship.

I think the idea of a permanent presence on Mars al la Antarctica (these places have quite a lot in common actually) is a good idea, I just don't think a proper colony with people being born, living out their lives and dying there is viable - unless I'm wrong about the gravity thing, which I'm very happy to be.

I did.

I'm not so sure. If you can go 0.8 or 0.9c with some futuristic proposition drive then I think the time dilation gets to the point where the travellers should live to see their destination. The logistical challenge for going to nearby stars is the same as the one for going to distant stars; you just need to be able to build a ship that'll keep people alive for years or decades.

But you wouldn't be expanding your own civilisation that way, just starting new ones.

Your other option is you colonize nearby habitable exoplanets, wait a couple of centuries until they're supporting developed cultures of their own then *they* send out colony ships to worlds near to them and so on and so on. After a few million years of this, your dudes are probably on a significant %age of the milky way.

Regarding the gravity thing, obviously it's all unknown at this point. But from what I've read, most designs for, say, rotating spacecraft, aim for a much lower gravity and it's assumed/hoped that this will be enough. Most problems come from a lack of gravity (fluids not going to the proper places etc.) and are thought to be much less of a problem if you have at least some gravity. But of course this has not been tested yet. Obviously an Antarctica like base would also come before any actual colonization. But still, any problem you'll encounter trying to colonize other planets in our solar system are likely also encountered on exoplanets (unless you're extremely lucky and find a copy of Earth nearby), so I think it makes sense to try it here first. If you can do it here, you might be able to do it in another solar system. but if you can't even do it here, where the distances are relatively short and there's at least some prospect of direct aid, or even evacuation if it all goes wrong. So I think colonization in our solar system is basically an essential step to colonizing exoplanets. And even if you don't want to go terraforming and colonizing planet surfaces, you probably still want to try it out in nearby space before flying to the next solar system with nothing more than hope to try and make it.

And again, that big 'if' in 'if you can go 0.8 or 0.9c', it's a big if to speculate about future propulsion. I'm a bit rusty on time dilation etc. so I'm not sure if you're correct on that.

Lastly, if you're not going to expand your civilization but starting a new one.. Bluntly put, would a society be willing to pour vast resources into a project like that, which does not have any added benefit for their own civilization? Sure, it'd be cool, but would that warrant the presumably vast expenses? The Apollo project took NASA funding to almost 5% of US budget, but at least had direct benefit and prestige in the cold war.

Regarding the gravity thing, obviously it's all unknown at this point. But from what I've read, most designs for, say, rotating spacecraft, aim for a much lower gravity and it's assumed/hoped that this will be enough. Most problems come from a lack of gravity (fluids not going to the proper places etc.) and are thought to be much less of a problem if you have at least some gravity. But of course this has not been tested yet.

Astronauts on the ISS currently do 6 months tours in microgravity and this is enough for noticeable but not serious health effects. For spacecraft that produce gravity, but lower than earth's, will presumably mitigate health problems to the extent that missions measured in years will be possible without astronauts suffering too badly. But over the course of human-life time, I believe there is a good chance that 0.4g is going have an impact on people living on Mars and people born on Mars. No one will want to go and live and have children on Planet Osteoporosis.

Obviously an Antarctica like base would also come before any actual colonization. But still, any problem you'll encounter trying to colonize other planets in our solar system are likely also encountered on exoplanets (unless you're extremely lucky and find a copy of Earth nearby), so I think it makes sense to try it here first.

Here's the thing: I don't think any space colony has a hope of being sustainable unless it has a genuine economic reason to exist; after the first few generations the population will just drift away otherwise. "to try it out for when we do it on exoplanets" is not a genuine economic reason; the people are there for the sake of being there, not because there's some advantage to being there. I don't say such a thing couldn't or shouldn't happen, I can picture NASA or someone doing exactly that, a little model community on Mars made up of volunteers to study long term effects of life on Mars on human beings. But that wouldn't be a true, self-sustaining colony that could survive if something bad happened to the Earth.

Lastly, if you're not going to expand your civilization but starting a new one.. Bluntly put, would a society be willing to pour vast resources into a project like that, which does not have any added benefit for their own civilization? Sure, it'd be cool, but would that warrant the presumably vast expenses? The Apollo project took NASA funding to almost 5% of US budget, but at least had direct benefit and prestige in the cold war.

Society isn't a monolith. Some entities in society made decide they just don't like the way things are being run around here (here = Sol) and take off in a generation ship.

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Astronauts on the ISS currently do 6 months tours in microgravity and this is enough for noticeable but not serious health effects. For spacecraft that produce gravity, but lower than earth's, will presumably mitigate health problems to the extent that missions measured in years will be possible without astronauts suffering too badly. But over the course of human-life time, I believe there is a good chance that 0.4g is going have an impact on people living on Mars and people born on Mars. No one will want to go and live and have children on Planet Osteoporosis.

I always got the impression that a lot of the biggest problems with lower gravity stem from expecting the astronauts to return to Earth. If there's no such expectation, then it's not as big a deal if you adapt to lesser gravity.

Here's the thing: I don't think any space colony has a hope of being sustainable unless it has a genuine economic reason to exist; after the first few generations the population will just drift away otherwise. "to try it out for when we do it on exoplanets" is not a genuine economic reason; the people are there for the sake of being there, not because there's some advantage to being there. I don't say such a thing couldn't or shouldn't happen, I can picture NASA or someone doing exactly that, a little model community on Mars made up of volunteers to study long term effects of life on Mars on human beings. But that wouldn't be a true, self-sustaining colony that could survive if something bad happened to the Earth.

A Martian space elevator can be built with currently existing materials.

Totally agree that new colonies won't survive without an economic reason to exist. We don't want Space Detroit.

There are some that aren't, but I think they are in the "mitigated by being in any kind of gravity at all" kind, like your eyesight getting messed up. So you may be right.

I always envisioned that with a fully developed Mars colony, people could travel and trade between Mars and Earth for trade and leisure fairly freely which is kinda messed up if people adjusted to Mars aren't good for anything once they get to Earth - but I supposed that's not actually *necessary*

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Though wings and parachutes have their adherents and their advantages, I’m a huge fan of rocket-powered vertical landing. Why? Because — to achieve our vision of millions of people living and working in space — we will need to build very large rocket boosters. And the vertical landing architecture scales extraordinarily well. When you do a vertical landing, you’re solving the classic inverted pendulum problem, and the inverted pendulum problem gets a bit easier as the pendulum gets a bit bigger. Try balancing a pencil on the tip of your finger. Now try it with a broomstick. The broomstick is simpler because its greater moment of inertia makes it easier to balance. We solved the inverted pendulum problem on New Shepard with an engine that dynamically gimbals to balance the vehicle as it descends. And since New Shepard is the smallest booster we will ever build, this carefully choreographed dance atop our plume will just get easier from here. We’re already more than three years into development of our first orbital vehicle. Though it will be the small vehicle in our orbital family, it’s still many times larger than New Shepard. I hope to share details about this first orbital vehicle this year.

“Humanity's greatest advances are not in its discoveries, but in how those discoveries are applied to reduce inequity.”
— Bill Gates

SpaceX are years and years ahead of Blue Origin, what they've achieved so far with New Shepard is where SpaceX were with Grasshoper back in '14. They just didn't bother to take it up to the Karmen line. And Blue Origins patent bellendery is more than a bit off putting.

That said, their development approach seems rather different to SpaceX's rapid and public iterations so I would not be surprised if they began gaining ground on SpaceX rather quickly. Their long term goals seem a little different, too, Blue Origins wants to facilitate access to Earth orbit for people, SpaceX wants to start a colony on Mars. So I wish them well, but they really haven't done much of anything yet.

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Yeah, all Blue Origin have at this point is test hardware, they have yet to make orbit which is something SpaceX achieved back in 2008.

However, if their goal is, quote, "millions of people working and living in Earth orbit" the slow approach makes a certain amount of sense - the Space Hotels and orbital industries they apparently want to service do not yet exist.

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I don't really get people who think it's ever going to be economical to have SF-level populations in orbit. Even with wildly optimistic assumptions, SpaceX is still probably going to have costs on the order of a few hundred dollars per pound to get to LEO let alone GTO. That's dirt cheap by many standards, meaning satellite launch will be much easier and relatively cheap. The key word here, though, is 'relatively'. It will still take large amounts of money to put people in space on an absolute scale, and we're never going to have millions of people traveling there on a regular basis without a step change in technology (e.g. elevators or catapults or the like)

Cheaper launch costs are great, and I see them being valuable for developing outer space industries - e.g. Trojan asteroid capture and mining, space stations and crewed missions for exploration, etc. But while Earth orbit and the solar system might get a bit more crowded, it's almost entirely going to be unmanned. Space tourism and the like will be the preserve of the very rich.

"When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." - Werner Heisenberg (maybe)

I don't really get people who think it's ever going to be economical to have SF-level populations in orbit. Even with wildly optimistic assumptions, SpaceX is still probably going to have costs on the order of a few hundred dollars per pound to get to LEO let alone GTO. That's dirt cheap by many standards, meaning satellite launch will be much easier and relatively cheap. The key word here, though, is 'relatively'. It will still take large amounts of money to put people in space on an absolute scale, and we're never going to have millions of people traveling there on a regular basis without a step change in technology (e.g. elevators or catapults or the like)

Cheaper launch costs are great, and I see them being valuable for developing outer space industries - e.g. Trojan asteroid capture and mining, space stations and crewed missions for exploration, etc. But while Earth orbit and the solar system might get a bit more crowded, it's almost entirely going to be unmanned. Space tourism and the like will be the preserve of the very rich.

Agreed, though the modular smallish hotels like Bigelow Aerospace suggests do make sense, as a vacation for the (very) rich. It'd probably be a lot cheaper than buying your way onto MIR, and people did that (just looked it up, they expect about $30 million for the flights, and $25 million for a 2 month lease of a third of their station - very pricy, but I bet some people are willing to pay that, and it would presumably get cheaper over time). But yes, more importantly it can be used for any commercial use in space, while being cheaper and more available than, say, the ISS.

- Just looked up what people previously paid for orbital tourism, seems to be $20million - $40 million, for maximum 15 days.

I don't really get people who think it's ever going to be economical to have SF-level populations in orbit. Even with wildly optimistic assumptions, SpaceX is still probably going to have costs on the order of a few hundred dollars per pound to get to LEO let alone GTO. That's dirt cheap by many standards, meaning satellite launch will be much easier and relatively cheap. The key word here, though, is 'relatively'. It will still take large amounts of money to put people in space on an absolute scale, and we're never going to have millions of people traveling there on a regular basis without a step change in technology (e.g. elevators or catapults or the like)

Well, I don't think people are going to be commuting to LEO any time soon, but your company might pay to send you up for 6 or 12 months to work on some project they have going on up there.

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